Compilare: user.cpp: In function ‘long unsigned int nr_divizori(long unsigned int)’: user.cpp:21: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:47: warning: comparison between signed and unsigned integer expressions user.cpp:50: warning: comparison between signed and unsigned integer expressions user.cpp:51: warning: comparison between signed and unsigned integer expressions user.cpp:63: warning: comparison between signed and unsigned integer expressions user.cpp:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:43: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result